Direct measuring TPMSs are becoming a common feature in modem vehicles. These systems consist of two main system components: sensing modules placed inside each wheel and a central reception unit placed inside the vehicle. A sensing module of a direct measuring TMPS has three main contributions to the overall energy consumption. These are power down current between active operation, radio frequency (RF) transmission and sensor measurements. All known direct measuring TPMSs rely on locally stored energy in order to operate and transmit information. The stored energy is in the form of a battery or is accumulated in small amounts from the surroundings.
A problem with such TMPSs is how to minimize the total amount of energy needed for operation, thereby minimizing the overall cost, volume and weight of the sensing modules.